Work State the formula and units for calculating

Work * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

What is work? “When an object is moved by a force we say that work is done on the object by a force” The force is transferring energy to the object. The amount of energy transferred is equal to the work done on it. * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

Calculating work done Energy transferred = work done Work done = force applied x distance moved in direction of force W=Fxd W = work done in joules, J F = force in newtons, N d = distance moved in direction of the force, m * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

How much work? A builder pushes a wheelbarrow a distance of 10. 0 m across flat ground. He uses a force of 100 N so how much work does he do? Work done = force applied x distance moved in direction of force W =Fxd = 1000 x 10 J * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

How much work? Eddie Hall pushed a 2 tonne truck just over 20 metres in 18 seconds. How much work did he do? W = F x = 20, 000 x 20 = 400, 000 J d * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

Which one of these involves doing the most work? • Write down a definition for work • For each write down how you determined the work done and what the final value was 1. Lifting a (full) mug of tea from the desk to your mouth 2. Opening the classroom door 3. Pulling back your chair to sit down 4. Writing 10 metres of English work 5. Climbing on the desk to close a window * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

Friction Rub your hands together. What happens? Your muscles do work to overcome friction and this is transferred into heat energy Brake pads become hot if you apply the brakes for too long. Friction between the brake and the wheel slows down the vehicle. Most of the energy is transferred into heat (and maybe some sound) * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

Q 1. (a) The weightlifter in the picture has lifted a weight of 2250 newtons above his head. The weight is held still. (i) In the box are the names of three forms of energy. gravitational potential kinetic sound Which one of these forms of energy does the weight have? . . . . . . . (1) (ii) What force is used by the weightlifter to hold the weight still? Size of force =. . . . N Give a reason for your answer. . . . . . . . . . . . (2) (b) To lift the weight, the weightlifter does 4500 joules of work in 3. 0 seconds. Use the following equation to calculate the power developed by the weightlifter. Show clearly how you work out your answer. . . . . . . . . . . . . . . . . Power =. . . Watts (2) (Total 5 marks) * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

M 1. (a) (i) gravitational potential accept gravitational accept potential 1 (ii) 1 2250 (N) forces must be balanced or forces are equal and opposite do not accept because it is not moving do not accept ‘equilibrium’ by itself do not accept ‘it is not balanced’ do not accept ‘forces are equal’ do not accept ‘forces are the same’ 1 (b) 1500 1 mark for correct substitution 2 [5] * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples

E 1. This question was generally answered well although very few achieved the maximum 5 marks. The principal error was in part (a)(ii) where statements purely confirming the correct choice of 2250 N could not be credited. Candidates failed to state that if the weight is held still then the force used by the weightlifter must act in the opposite direction to the downward force of the weight. * ** *** State the formula and units for calculating work Extract information from questions to calculate work Calculate work using real examples